William Adair from Pennsylvania

I am looking for information on William Adair possibly born in Pennsylvania approx 1827.His father was also William Adair and his mother Mary McAlister.He died in Australia in 1909.The family was originally from Co Antrim, Ireland - but William lists on the church record of his marriage (in Australia 1854) that he was born in Pennsylvania.Does this tie in with anyone else's research - or has anyone come across family members moving from US to Australia?